Is my Battery OK?

isaacs

Petty Officer 2nd Class
Joined
Oct 15, 2013
Messages
153
My boat lives in my driveway and had not been used in about five weeks. Yesterday when I hooked it up I realized I had no 12V power. I assumed that I had left my depth finder on and that would have drained the battery which I bought new this season.

I jump started the boat (still in the driveway) and ran it for about 20 minutes. When I got to the launch, it just barely started. I proceeded to my destination, 1/2 hour, but when I got there I tried restarting the engine and it was completely dead. This seemed wrong so I checked the connections at the battery and sure enough one of the wingnuts was loose. I don't know if it was loose all along or I knocked it loose earlier with the jumper cables. After I tightened up the wingnut the boat ran perfectly for the rest of the day including my 1/2 hour run back to the launch.

I decided it would be a good idea to hook up a charger overnight just to make sure I was charged. My charger is a common Exide one with the lights that bounce back and forth between "charging" and "charged" as the battery charges. The light stayed on "charging" for several hours and only after I got up this morning was it starting to bounce to "charged" which would indicate that the battery was pretty low.

My questions are: Why did the engine start perfectly if it was that low? Are the alternators in these boats so puny that a 1/2 hour run wouldn't be enough to get the battery pretty close to full? My dash gauge shows 13 volts when I am running so I would think that's it's charging OK.

Thanks to anyone who took the time to read all this!--Bob

Bayliner 2150 Capri, 5L Mercriuser Alpha 1, Gen 2
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
13V while running would be very low, it would typically be over 14V.

Take the battery in and have it load tested.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
51,258
The alternators are not that large

Loose wingnut could have carbon arced the terminal and toaseted the alternator

Battery could be toast

Clean all the battery cable connections, have both your alternator and battery tested
 

isaacs

Petty Officer 2nd Class
Joined
Oct 15, 2013
Messages
153
Thanks for the replies. The battery seems to have taken a charge--it's behaving like a good battery usually does on my charger. As for the alternator, I'm not sure how accurate the dash gauge is; I believe it has read 13V since day one. All connections are nice and clean.

In order to test the alternator, I would have to remove it and take it to an auto parts store right? Could I check the voltage at the battery while I'm under way with a proper volt meter and look for 14 volts?
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
With a charged battery it should put out over 14 volts, but don't trust a gauge on the dash, use a multi meter and check at the battery.
 

Brandon5778

Petty Officer 2nd Class
Joined
Jul 9, 2016
Messages
141
An alternator, to my understanding, isn't supposed to charge up a dead battery. It is meant to maintain your battery.
 

isaacs

Petty Officer 2nd Class
Joined
Oct 15, 2013
Messages
153
An alternator, to my understanding, isn't supposed to charge up a dead battery. It is meant to maintain your battery.

Yeah, I think I just verified that! I'm headed out onto the river today, perhaps I'll take a meter with me.

If I get stuck out there, no biggie. Niagara Falls is just a few miles downstream and that will take care of everything!
 
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